Barbra Streisand told a sell-out Berlin concert crowd on Saturday that she was delighted to perform in Germany for the first time after turning down several invitations in the past. German media have linked the Jewish star’s refusal to sing there previously to Germany’s responsibility for the Holocaust and had hailed her decision to appear.

Streisand quickly warmed to the enthusiastic audience of 18,000 that gave her more than a dozen standing ovations. “I’m so very happy to be in your country,” Streisand said, speaking in flawless German. “It’s exciting for me to be here, too,” Streisand added before listing some of the things she likes about Germany – from currywurst and apple strudel to Beethoven and Bach. She recited a Goethe poem, which she said was a lifelong favourite.

“Germany has always been a place where you buy a lot of my records. I feel very good here. I’m always amazed how music can transcend all our differences. Even though I may complain about certain things, I’ve come to look at the glass as half full. I’m really glad to be in your city – it’s filled with culture…and the deserts I love,” Streisand said in the open-air Waldbuehne arena, next to Berlin’s Olympic stadium used for the 1936 Olympics and tarnished by its association with the Nazis.

Paul Spiegel, late leader of Germany’s Jewish community, said he had made repeated appeals to her to come, and, before dying last year, Spiegel blamed her refusal on the Holocaust. “Barbra Streisand was the only one,” Spiegel said, when asked if artists had reservations about Germany. Spiegel, a top German talent agent, said he could understand her stance.

Streisand, one of the best-selling female artists of all time, is on a six-week, eight-city tour through Europe. Born in New York to Jewish American parents in 1942, according to online biographies, Streisand has never played outside North America except for London and Australia. The 65-year-old singer did not want to comment on her reasons for not coming to Germany in her career before. But in a statement to Reuters on Friday she had said: “Germany is a very different place than it was before World War Two.”

“Thank you for coming to Berlin!” shouted one fan at one point late in her two and a half hour long show. “It’s my pleasure – I’m thrilled to be here,” she replied.

This year rap and hip-hop sales are down 33 per cent, double the decline of the CD album market overall, which is under pressure from music download sites such as iTunes, where fans can buy individual songs.

In 2006, rap sold 59.1 million albums, down 21 per cent from 2005. Not one rap album made the American top 10 sellers of the year – a list headed by the saccharine tunes of the soundtrack to Disney’s made-for-television High School Musical. The bad boys of rap are now trailing the cowboys of country and the headbangers of heavy metal.

Since rap’s apotheosis five years ago, when Eminem’s album The Eminem Show topped the American charts with 7.6 million sales, no rapper has come close to emulating his success.

Rap has been deserted by many white fans and middle-class blacks, apparently tiring of the “gangsta” attitude to women, racism, violence and bling – the gold rings and medallions that have made hip-hop a byword for vulgarity.

“The public has made a choice. They’re saying, ‘We do not want the nonsense that we see and hear on radio, and we are not putting our money there’,” said KRS-One, a rap legend from the Bronx. “Rap music is being boycotted by the American public because of the images that we are putting forward.”

Tom Vickers, a former talent spotter for Capitol/Mercury records said: “Rap has gradually degenerated from an art form into a ring tone. That’s why we’re seeing this backlash. There’s only so much bling the public can take.”

The early pioneers of rap are also seen to have sold out. Snoop Dogg, once famed for his ghetto lyrics, is now helping to advertise Pony trainers while 50 Cent is pushing grape-flavoured vitamin water. The rap artist Nas bemoans the decline on his new album Hip Hop Is Dead, complaining that everyone sounds the same and that they have forgotten their roots.

No one embodies the decline of rap like Marion “Suge” Knight, the man who created Death Row Records and became known as the John Gotti of hip-hop. When Knight, reputedly a member of the LA gang the Bloods, helped mastermind the careers of Dr Dre, Snoop Dogg and Tupac Shakur, his company boasted annual sales of $200 million (£100 million) and the monicker “Motown of the Nineties”.

Now he is an ex-convict, a bankrupt who is $137 million in debt and facing a civil trial in which the family of murdered rap star the Notorious B.I.G. claim that he was gunned down in 1997 by hitmen hired by Death Row as part of an East Coast-West Coast rap feud. Now the bad boy of rap is planning to withdraw the entire Death Row back catalogue and bleep out each and every instance of the word “nigga” in its songs. “To me, it’s never too late to change,” he told The Washington Post last week.

Earlier this year, the radio “shock jock” Don Imus sparked a media storm by referring to black members of the Rutgers ladies basketball team as “nappy headed hos”, a derogatory term for unkempt prostitutes. The fury that ensued cost Imus his job but immediately prompted claims that an ageing white man is judged by different standards from the “gangsta” rappers who use such terms with abandon.

The Democrat presidential candidate Barack Obama joined the conservative Fox News channel in calling for a crackdown on rap lyrics.

Hip-hop mogul Russell Simmons, who made millions co-founding and then selling the Def Jam label, called a meeting of music industry executives shortly afterwards and called for the words “nigga”, “bitch” and “ho” to be bleeped out of radio versions of songs.

The New York civil rights leader, the Rev Al Sharpton, protested outside the offices of leading record labels and met executives from Universal, Warner and Sony Music, who control 90 per cent of the rap market between them. He declared: “We plan to continue to march until those three words are gone.”

In the rush to condemn, the leading black magazine Ebony removed the rapper Ludacris from its cover. Verizon records then dropped Senegalese-American hip-hop star Akon after video footage surfaced of him simulating sex with an underage fan on stage.

For many, though, this capitulation to mainstream taste is another sign that rap is dying. An unrepentant 50 Cent said he had no intention of cleaning up his lyrics. “Music is a mirror,” he said, “and hip-hop is a reflection of the environment we grew up in. If I ask you to paint a picture of the American flag and not use the colour red, you’re going to have a difficult time.”

But others see in this reappraisal a renewal of the genre. Michael Dyson, professor of African-American and Religious Studies at the University of Pennsylvania said: “The most powerful sign that hip-hop culture is alive is the withering critique from within about the industry. Horrible hip-hop must die so that regal hip-hop can live. Hip-hop is dead; Long live hip-hop.”